The frying pan has a very simple structure: a bottom (metal disc) and an annular board. Add a handle and a cover. Its shape remains unchanged from the earliest times (except for some insignificant details). So far, the frying pan has been improved by using better materials, for instance, non-stick coatings, or by changing the handle shape and the cover design. 
However, the cooking process also attracted attention of inventors. While frying, you must turn cutlets from time to time. To do this, the frying pan board is used. Inventors replaced the conventionally conical shape of the board with toric. Now it is enough to push a cutlet up on the board surface and it will turn over following the geometrical laws.
But there is a contradiction. here. It is easy to turn something on such a frying pan, but it is much more difficult to extract it from the frying pan because of the board's shape.

This contradiction can be resolved in space. For this purpose the board is made traditional – conical – on one side of the frying pan and toric on the other side.